Astronauts are protected from the hostile environment of space by means of special clothing given the general name pressurized spacesuits. Such suits have in common the function of protecting an astronaut from the effects of extreme temperatures, while dumping metabolically-generated heat and providing a constant supply of air for breathing. However, such suits also have in common the drawback of very severely limiting the dexterity of astronauts when handling objects, and in general when interacting with the environment.
In order to provide a comfortable environment for an astronaut, two different approaches have been followed. The first approach consists in making rigid pressurized suits made up of rigid cylinders for containing air and interconnected by joints enabling relative motion of the astronaut's limbs, with the limbs and the body being encased in rigid and substantially cylindrical elements.
The second approach seeks to provide flexible pressurized suits constituting an airtight covering that fits the astronaut's body.
However, both rigid and flexible spacesuits suffer from drawbacks due to the requirement that astronauts should not do thermal dynamic work on the air that surrounds them whenever they move:
in rigid spacesuits, this means that the joints must be "constant-volume" joints; and
in flexible pressurized spacesuits this means that cables or other equivalent means must be provided to limit spacesuit movement.
These drawbacks are especially severe in gloves. It is particularly difficult to make constant-volume joints that are as small as knuckle joints, and as a result it still remains difficult for astronauts to perform accurate manual tasks.
There thus exists a particular need in this field for pressurized gloves for astronauts providing improved dexterity, i.e. improved tactile feedback, and thereby extending the range of handling operations that can be performed, and this implies that gloves must be lightweight in design and easy to use while nevertheless being economically viable.
One principle for developing a glove to satisfy the above-mentioned requirements for use in a pressurized spacesuit, was proposed towards the end of the 1960s. This principle consists in counterbalancing the internal pressure of the tissues of the human body by mechanical means which replace the pressure exerted by air, be that the air to which the human body is normally subject on Earth or the air that exists inside a pressurized suit. The mechanical means are not specified a priori.
A spacesuit glove proposed in the prior art based on this principle is an elastic skin-tight glove which presses against the skin of the astronaut's hand (sometimes called a "skinsuit" glove), and the glove is designed so that the pressure applied to the astronaut's hand by the elastic tightness of the glove is substantially equal to the pressure that would be exerted on the hand by air in a conventional pressurized suit. This prior art glove is thus based on the concept of "elastic pressurization" and enables hybrid pressurized suits to be made, i.e. suits in which the body of an astronaut is pressurized in conventional manner whereas the hands are pressurized by means of elastic gloves as described above. To this end, a hybrid spacesuit includes an interface between that portion of the body which is pressurized normally and each hand which is pressurized elastically (further detail on the prior art technique can be found from the scientific article "Advanced spacesuit glove design" published in 1985 by the Massachusetts Institute of Technology and NASA, in IAA Conference Proceedings issue 12, pages 469 to 488).
However, although an astronaut's manual dexterity is considerably improved by elastic gloves compared with conventional pressurized suits, it is clear that this dexterity is far from being comparable to that which an astronaut would have with bare hands, which is naturally the ideal situation.
U.S. Pat. No. 3,363,266 discloses an internally pressurized spacesuit comprising means for increasing the mobility of a limb portion, such as an arm section adapted to receive the arm of a wearer of the suit, with the wearer's hand being enclosed within a pressurized glove. These means comprise an annular seal of stretchable material and a plug valve applied on the arm section. The seal separates a chamber defined in the arm section from the remainder of the suit, and the valve puts the chamber into communication with the remainder of the suit under normal conditions, or with the space environment (thus depressurizing the chamber) when a need exists for facilitating flexing of the arm section including the glove. The seal is attached both to the arm section including the glove and to a sleeve surrounding the remainder of the wearer's arm, and the seal is compressed in response to the pressure differential between the chamber and the remainder of the suit.
However, this prior solution suffers from several drawbacks, including the need for the pressure in the chamber and the glove to be restored periodically so as to relax the seal about the arm and reestablish proper blood circulation, and also the existence of potential safety hazards due to the undesirable physiological effects produced by the near vacuum which may occur in the chamber and the glove in the event of failure of a backpressure valve provided for maintaining a residual pressure differential between the space environment and the chamber.
The object of the present invention is thus to provide a pressurized suit fitted with elastic gloves suitable for imparting improved dexterity to the hands of an astronaut and constituting and acceptable compromise between the two extreme conditions represented by the hands of the astronauts being subjected to the same pressure as the remainder of the body or else to no pressure. The solution provided to this end by the present invention is based on the present physiological understanding that astronauts can work for relatively long periods of time with their hands at a lower pressure than the remainder of their bodies, and it also takes account of the fact that astronauts require improved dexterity only when performing special tasks e.g. when handling small-sized objects such as pliers, screwdrivers, etc., or when handling electrical apparatuses, e.g. setting up electrical connections, and in general handling electrical cables. In contrast, such high dexterity is not required when performing operations on large-sized structures.